1. Field of the Invention
The present invention relates to an organopolysiloxane gel composition, which yields a cured product (silicone gel) upon an organopolysiloxane addition reaction, and can be used particularly favorably for protecting ICs and hybrid ICs, and for encapsulating power modules and the like.
2. Description of the Prior Art
Silicone gel compositions are addition reaction-curable organopolysiloxane compositions, which comprise an organohydrogenpolysiloxane having hydrogen atoms bonded to silicon atoms (namely, SiH groups), an organopolysiloxane having alkenyl groups such as vinyl groups bonded to silicon atoms, and a platinum-based catalyst, and which yield a cured product via an addition reaction of the SiH groups to the alkenyl groups such as vinyl groups. The silicone gels of these cured products exhibit excellent levels of heat resistance, weather resistance, oil resistance, cold resistance and electrical insulation, and also exhibit low elastic modulus values and low levels of stress, and as a result, they are widely used in the protection of vehicle-mounted electronic components and household electronic appliance components. In recent years, with the ongoing trend towards smaller and lighter electronic componentry, the density of IC components, and the density of the wiring such as wire bonding used to connect these IC components to substrates have continued to increase. Conventional silicone gel compositions are of comparatively low viscosity, and therefore tend to exhibit favorable flow properties, but the obtained silicone gels lack resistance to the types of deformations caused by external stresses such as vibrations, and internal stresses caused by the expansion and contraction that accompany variations in temperature, and have been known to suffer from gel rupture or internal cracking.
Examples of compositions in which the above-mentioned organohydrogenpolysiloxane has a branched main chain structure have already been disclosed in JP 2,510,577 B (Patent Document 1) and JP 2,849,027 B (Patent Document 2), but all of the gels disclosed in these documents exhibit a penetration value as prescribed in JIS K-6249 that exceeds 200, meaning that if subjected to a large amount of stress, the gel is prone to rupture.
[Patent Document 1] JP 2,510,577 B
[Patent Document 2] JP 2,849,027 B